Mirrors used in telescopes are often used with their optical axis in a position which is horizontal or nearly horizontal and it is well known that under such conditions the mirror tends to suffer from distortion phenomena due to the effect of gravity, and that such phenomena increase with increasing mirror diameter and with decreasing mirror stiffness.
Various means are used to prevent or mitigate this distortion phenomenon, and such means include, in particular, means for providing lateral support to the mirror via counterweights or air cushions.
Another technique consists in making a mirror as a honeycomb structure with walls delimiting hollow cells or cavities, with said structure having a front face on which a thin reflecting front wall is fixed, and a rear face on which a thin rear wall is fixed. The resulting assembly constitutes a mirror which is substantially lighter than a solid mirror.
However, because it is less rigid than a solid mirror, such a mirror is even more subject to deformation, and when attempts are made to avoid such deformation by means of counterweight systems or air cushion systems the overall weight of the assembly is increased, thereby losing at least some of the advantages due to the light weight of the mirror itself.
Preferred implementations of the present invention provide a reduced weight mirror which is less subject to distortion than is a solid mirror.